Electric safety plug



April 24, 1934. c. E. GILBERT ELECTRIC SAFETY PLUG Fild Jan. 8, 1952 IN V EN TOR.

W ATTORNE s.

Patented Apr. 24, 1934 ELECTRIC SAFETY PLUG Charles E. Gilbert, New York, N. Y., assignor to Gilbert & Hertz Inc., a corporation of New York Application January 8, 1932, Serial No'. 585,464

3 Claims.

Among the objects of my invention is that of an electric plug of inexpensive and rugged construction to which insulated wires may be easily and quickly connected without removal of the insulation and which will hold such wires with great tenacity and with less danger of rupture than plugs of ordinary construction.

A further object is a plug to which the wires may be attached without the use of tools, even a screw driver being unnecessary. This together with the fact that the insulation need not be removed makes the plug of great convenience to the average householder possessed of little or no mechanical skill. It is practically impossible to connect wires to my plug in an improper manner or so that short-circuiting can occur.

In the accompanying drawing I have selected two forms of my plug for purposes of illustration without thereby intending to limit my invention w thereto. Of these Figure 1 is a view in perspective of one form of the plug of my invention;

Fig. 2 is a plan view of the same plug looking from the under side with the prongs and prong 943 retaining disk removed to disclose the internal construction of the body;

Fig. 3 is a view of one of the contact members; Fig. 4 illustrates the retaining disk; Fig. 5 shows the spring whereby the retaining 39 disk is held in position on the body;

Fig. 6 is a cross-sectional view of the plug along the line A-A of Fig. 2;

Fig. 7 is a view in perspective of my plug in which another form of retaining disk is employed illustrating the manner in which this disk is applied to the plug body and Fig. 8 is a view of this type of retaining disk. The contact element 1 illustrated in Fig. 3 combines in a single piece the prong for con- 49 nection to the electrical outlet and the means whereby the insulated wire is connected thereto. This entire element may be stamped from any suitable conducting material of suitable thickness in a single flat piece and by a single operation. No rivets or binding posts are employed for either holding the element in position or for retaining the wires so that extreme ease and economy of manufacture is attained.

This contact element includes the prong 2 sur- 0 mounted by a wire gripping jaw 3. A slot 4 runs from the top of the element to a point near the end of the prong section where, preferably, it is enlargecl'to form the customary aperture 5 for engagement with the usual projection in the contact-member of the outlet. This shape also permits the two sides of the element to spring apart somewhat when inserting the wire without otherwise distorting it. It will be noted that the slot 4 is slightly offset at the wire gripping section and that the shoulder 6 thus formed is given a pointed upwardly projecting shape. By this means the distance to which the wire may be forced into the jaw is limited.

In one side of the wire gripping jaw serrations or teeth a are provided which constitute the actual insulation piercing and contact making means. For convenience, in inserting the wire I prefer to chamfer the corners 9 and 10 and I also chamfer the corners 11 and 12 to assist in inserting the contact member into its receptacle.

The body of theplug with which this contact member is combined is of the same general dimensions and external appearance as that of an ordinary plug, as will be seen from Fig. 1. The internal construction, however, is quite different and is novel.

As will be seen from Fig. 2 which is a view of the body looking from beneath or from the prong end, the body 13, which may be molded in one piece of bakelite or other suitable non-conducting material, is provided with two recesses 14 and 15 of double keyhole shape symmetrically positioned on either side of the center. The width of the rectangular portion of each recess is slightly greater than the thickness of the wire g pping 35 end of the contact member so that the wire gripping end when positioned in the slot will fit snugly but may be removed without difliculty. The length of each recess is slightly less than the normal width of the contact member at the wire gripping end, so that its insertion into the recess will cause the jaw to close and the teeth 8 to. positively penetrate the insulation of the wire. In depth, each recess is substantially equal to the length of the contact member from the top to the shoulders 16.

A central aperture 1'7 afiords access for the electric cord to the interior of the plug. A transverse channel 18 intersects the round section of each recess and also the central aperture 17, the purpose of which will be later explained. The ends of channel 18 may also be extended as at 19 in a direction generally parallel to the periphery of the body.

The remaining element of my plug is the disk 20. In the form shown in Fig. 4 this is a simple disk of insulating material generally similar to that now employed to cover the bottom of the ordinary plug and similarly provided with two slots 21 and 22 through which the prongs project. However, in my plug the purpose of this disk is not merely to close the body, but also serves to retain the contact prongs within the plug through the engagement of shoulders 15, 16 with the inner face thereof. To this end I provide a means for positively retaining the disk in this position. The means referred to is shown in Fig. 5. It consists of a fiat spring 23 of the shape shown, which is slipped over the disk 20 and then up through apertures 24 and 25 (Fig. 2) until its hooked ends 26 and 27 engage over shoulders 28 formed in the body of the plug. Fig. 1 illustrates this to best advantage. The outwardly projecting tips 29 of the spring provide a means whereby it may be easily disengaged.

It will be noted that the bottom 30 of spring 23 is cambered. I prefer this form ofspring as it insures that the disk will be held firmly in position and also that any slight variations in the length of the sides of thespring or of the apertures 24 and 25 will not affect the application or the removal of the spring. Also, I prefer that the angles 30 and 31 of the spring should be slightly acute and that the shoulders 28 of the body be shaped to correspond since by this means once the spring is in position it cannot be disengaged by any strain upon the prongs or the disk, but will, on the contrary, be more securely retained by any such strain.

This completes the description of one form of my plug. It will be noted that it consists of five wholly separate parts, a body, two contact elements, a disk and a spring; that each part may be stamped or molded in a single piece by a single operation and that no screws or rivets are employed.

To assemble the plug and connect it to an electric cord the end of the cord is passed through the central aperture 17. The woven insulation surrounding both wires of the cord is then slipped back to expose the two insulated wires within. The end of one of these insulated wires is then forced sidewise into the slot 4 of contact member 1. This will cause the wire gripping jaw 3 to open slightly, thus creating sufl'lcient tension to hold the wire and the serrated edge 8 will pierce at least partially the insulation. The other wire is connected to the other contact member in a similar manner. The tooth 6 will insure that the wire is positioned in the wire gripping jaw 3 and will prevent its being forced further down into the lower part of the slot 4 forming a part of the prong end of the element.

The contact members are then pressed into their respective recesses 14 and 15, an operation made 'easy by the chamfered corners 11 and 12. The restricted size of the recesses will force the serrated edges of the wire gripping jaws into positive contact with the conductors within the insulation and, also, since the walls of the recesses and the sides of the wire gripping jaws are substantially parallel the contact members will be securely held in their recesses against any effort to remove them except by pulling on the prongs.

The free ends of the wires will obviously project somewhat from the sides of the contact members. When the members are seated in their recesses as above described, the free ends of the wires projecting from the contact jaws will be bent up and will rest in enlargements 31 of recesses 14 and 15, and if the ends are long enough in channels 18' and 19. It is therefore unnecessary to exercise any particular care in applying the wires.

They are simply pulled into the contact jaws somewhere near their ends.

Also, the wires on the other side of the jaws will be similarly bent and will rest in enlargements 32 of the recesses and channels 18. These bends added to the gripping power of the contact jaws will hold the wires firmly in place against any effort to pull them out by pulling on the cord.

Furthermore, the cushioning effect of the rubber insulation which has not been removed protects the wire from abrasions orbreaking at the ends.

The disk 20 is then passed over prongs 2 and seated against the bottom of the body which is preferably slightly recessed as shown, after which spring 23 is snapped into position as already described and as shown in Fig. 1 and the plug is ready for use.

The use of a spring may be dispensed with by employing another type of disk and by slightly modifying the body of the plug as shown in Figs. 7 and 8. Here the disk is provided with the additional slots 33 and 34 as shown in Fig. 8 forming two somewhat flexible tongues 35 and 36. At the tip of each tongue I provide a lug 37 which projects beyond the circumference of the disk. In the body 13, Fig. '7, I dispense with apertures 24 and 25 (Fig. 2) and add aperture 38 into which a lug 37 may be readily sprung to hold the disk in position. Since apertures 38 extend entirely through the body lugs 33 and 34 may be readily disengaged by pressing on their ends with the finger nails. To assist in this the body just above each recess opening may be cut away as shown at 40 in Fig. 7.

This form of disk also performs the dual functions of a contact member retainer and a closure for the bottom of one body the same as the type first described. j

In this form of my plug it will be noted that there are only four parts-the body, the two contact members and the retaining disk, each of which can be very inexpensively molded or stamped, as the case may be, by single operation. No further manufacturing operations are required to complete the plug. All of the usual operations of attaching the contact elements to the body, inserting binding screws, etc., are obviated and a plug is thus produced which may not only be manufactured with the greatest economy but which presents to the user the great advantage of being practically fool-proof and at the same time highly efiicient and durable.

I claim:

1. An electric plug consisting of a body having a recess-therein, a removable contact prong and.

wire gripping member the wire gripping portion of which is slidably seated in said recess, said member consisting of a strip of conducting material provided with a resilient jaw, means on said jaw to pierce the insulation of an insulated wire, said jaw fitting snugly into said recess in wire contacting position, and separate means for retaining said jaw within said recess. 1

2. An electric plug consisting of a body having a recess therein, a removable contact prong and wire gripping member the wire gripping portion of which is slidably seated in said recess, said member consisting of a strip of conducting material provided with a resilient jaw, means on said jaw to pierce the insulation of an insulated wire, said jaw fitting snugly into said recess in wire contacting position, and separate means for retaining said jaw within said recess, said rejaw to pierce the insulation of an insulated wire,

said jaw fitting snugly into said recess in wire contacting position, and separate means for retaining said jaw within said recess, said retaining means comprising a slotted disc having lugs projecting from the periphery thereof for engagement with corresponding recesses in the body,

' CHARLES E. GILBERT. 

